From 48b9bac87222f8915f0a58ffa59f65674574ed33 Mon Sep 17 00:00:00 2001
From: wb2osz <wb2osz@comcast.net>
Date: Fri, 13 Nov 2020 20:46:57 -0500
Subject: [PATCH] When decoding a third party traffic packet, decode the
 payload.

---
 src/decode_aprs.c | 54 ++++++++++++++++++++---------------------------
 src/symbols.c     |  2 ++
 2 files changed, 25 insertions(+), 31 deletions(-)

diff --git a/src/decode_aprs.c b/src/decode_aprs.c
index 3afa377..608ab18 100644
--- a/src/decode_aprs.c
+++ b/src/decode_aprs.c
@@ -116,7 +116,6 @@ static void aprs_morse_code (decode_aprs_t *A, char *, int);
 static void aprs_positionless_weather_report (decode_aprs_t *A, unsigned char *, int);
 static void weather_data (decode_aprs_t *A, char *wdata, int wind_prefix);
 static void aprs_ultimeter (decode_aprs_t *A, char *, int);
-static void third_party_header (decode_aprs_t *A, char *, int);
 static void decode_position (decode_aprs_t *A, position_t *ppos);
 static void decode_compressed_position (decode_aprs_t *A, compressed_position_t *ppos);
 static double get_latitude_8 (char *p, int quiet);
@@ -197,7 +196,22 @@ void decode_aprs (decode_aprs_t *A, packet_t pp, int quiet)
 	A->g_footprint_lon = G_UNKNOWN;
 	A->g_footprint_radius = G_UNKNOWN;
 
+// If third-party header, try to decode just the payload.
 
+	if (*pinfo == '}') {
+
+	  packet_t pp_payload = ax25_from_text ((char*)pinfo+1, 0);
+	  if (pp_payload != NULL) {
+	    decode_aprs (A, pp_payload, quiet);
+	    ax25_delete (pp_payload);
+	    return;
+	  }
+	  else {
+	    strlcpy (A->g_msg_type, "Third Party Header: Unable to parse payload.", sizeof(A->g_msg_type));
+	    ax25_get_addr_with_ssid (pp, AX25_SOURCE, A->g_src);
+	    ax25_get_addr_with_ssid (pp, AX25_DESTINATION, dest);
+	  }
+	}
 
 /*
  * Extract source and destination including the SSID.
@@ -362,11 +376,9 @@ void decode_aprs (decode_aprs_t *A, packet_t pp, int quiet)
 	      aprs_morse_code (A, (char*)pinfo, info_len);
 	      break;
 
-	    case '}':		/* third party header */
-
-	      third_party_header (A, (char*)pinfo, info_len);
-	      break;
+	    //case '}':		/* third party header */
 
+	      // was already caught earlier.
 
 	    //case '\r':		/* CR or LF? */
 	    //case '\n':
@@ -380,7 +392,12 @@ void decode_aprs (decode_aprs_t *A, packet_t pp, int quiet)
 
 
 /*
- * Look in other locations if not found in information field.
+ * Priority order for determining the symbol is:
+ *	- Information part, where appropriate.  Already done above.
+ *	- Destination field starting with GPS, SPC, or SYM.
+ *	- Source SSID - Confusing to most people.  Even I forgot about it when
+ *		someone questioned where the symbol came from.  It's in the APRS
+ *		protocol spec, end of Chapter 20.
  */
 
 	if (A->g_symbol_table == ' ' || A->g_symbol_code == ' ') {
@@ -2934,31 +2951,6 @@ static void aprs_ultimeter (decode_aprs_t *A, char *info, int ilen)
 } /* end aprs_ultimeter */
 
 
-/*------------------------------------------------------------------
- *
- * Function:	third_party_header
- *
- * Purpose:	Decode packet from a third party network.
- *
- * Inputs:	info 	- Pointer to Information field.
- *		ilen 	- Information field length.
- *
- * Outputs:	A->g_comment
- *
- * Description:	
- *
- *------------------------------------------------------------------*/
-
-static void third_party_header (decode_aprs_t *A, char *info, int ilen) 
-{
-
-	strlcpy (A->g_msg_type, "Third Party Header", sizeof(A->g_msg_type));
-
-	/* more later? */
-
-} /* end third_party_header */
-
-
 
 /*------------------------------------------------------------------
  *
diff --git a/src/symbols.c b/src/symbols.c
index bb29e4f..59a877d 100644
--- a/src/symbols.c
+++ b/src/symbols.c
@@ -659,6 +659,8 @@ void symbols_from_dest_or_src (char dti, char *src, char *dest, char *symtab, ch
 
 /*
  * When all else fails, use source SSID.
+ * This is totally non-obvious and confusing, but it is in the APRS protocol spec.
+ * Chapter 20, "Symbol in the Source Address SSID"
  */
 
 	p = strchr (src, '-');